using System;

public class Program

{

    public static void Main()

    {

    int x;

    x= int.Parse(Console.ReadLine());

        if (x>15)

        {

            Console.WriteLine(" class is open" );

            Console.WriteLine(" the number of participents is" + x);

        }

        else

        {

            Console.WriteLine("too few sign up");

            Console.WriteLine("you need " + (15-x) + "children to open the class");

        }

    }

}

​